Is model driven architecture worth it and what is the state of the art in the tooling?

Question

We have a recurring problem in our shop where we end up with 3 or 4 different representations of the same class/entity.

A java version, an xml version, a hibernate version, a json version... you get the point.

Obviously this creates maintenance problems.

Model driven architecture is probably more than this, but what I'd really like is a system that lets me define a class or an entity once, in one way, and then generate various representations. (maybe I am not using the correct terminology for this)

It really isn't that straight forward, of course, because let's say we have a java object that we want to turn into JSON for sending over the wire - there might not be an exact 1-1 correspondence between the members in the java object to the fields in JSON - there might be some optimizations, or whatever.

I've looked at things like AndroMDA and EMF in the past, and found them either lacking or clumsy. I do not know how they stack up these days, or what other systems there are.

What are SO's opinions on MDA and or meta-data driven programming? Have the tools become mature enough for serious consideration?

Thanks.

Answer 1

Check out Naked Objects

http://nakedobjects.codeplex.com/

and it's apache equivalent

http://isis.apache.org/index.html

The fact that both of these frameworks are almost unheard of should answer your question IMHO. I think ending up with inconsistent representations of the same objects indicates a flaw in your process, which isn't something you should try and solve with a framework.

Answer 2

As a contributor to both Naked Objects and Apache Isis, I can confirm the other answer from @dnellis74 given that these both address the issue of having multiple representations of the same thing; with these frameworks you write your domain object once, and then it is reflected automatically to the user as a persistence layer.

Of course, (and I would say this, wouldn't I?) I don't agree with @dnellis74 that the fact that these frameworks are little known means that they should be dismissed out of hand; you should decide for yourself.

One other point that might be of interest; both these frameworks are in the process of implementing the Restful Objects spec, which aims to expose your domain objects automatically via a RESTful API, and let you skin it or integrate with it as you see fit. The .NET impl is pretty complete, the Java impl is lagging a bit but even so has a demo that you can check out.

As for MDA, I was sceptical from the outset when it was first being tauted by the OMG, to the extent that I wrote an article about it on TheServerSide. I think I called it right.

Dan

Answer 3

To address your core concern, you can define a Java class for your domain object. Then, you can annotate the class with JAXB and Hibernate annotations. This way you have a single definition of your entity(the Java class) that can be output in various representations, JAXB for JSON and XML, Hibernate for persistence.